SUMMARY ? Project 4 Hazardous volatile organic compounds (VOC) have adverse impacts on human health. These compounds likely exhibit high spatial variability in urban areas because of the numerous emission sources (e.g. industrial, commercial, residential, traffic) and complex dispersion patterns. Thus, tools are needed to characterize the small-area variation of intra-urban VOC concentrations. Land use regression (LUR) modeling is a powerful tool for assessing spatial variability. It relies upon ambient measurements at a large number of sites and has been extensively used for pollutants such as nitrogen dioxide and particulate matter. However, relatively few studies have built LUR models for VOCs and in most cases the focus was traffic? related emissions of benzene and other compounds emitted by vehicles. Mobile platform measurements have recently been used to collect air quality data for LUR model-building. However, mobile monitoring of VOCs has not been used in LUR modeling because of measurement challenges. This project will develop a portable VOC monitor suitable for mobile platform measurements. Field studies will be conducted at urban- and neighborhood scales and the VOC data will be used for LUR model-building. LUR results will be used by another Center project to evaluate relationships between ambient VOCs and cardiometabolic disease. LUR results will also be used to examine relationships between VOC air quality and proximity to green space which might be an effective VOC remediation strategy. New tools will be developed to use mobile platform measurements to identify the location and strength of emission sources. This project is closely coupled to the Center?s primary objective to examine cardiometabolic effects of exposure to VOC Superfund chemicals. It will also have broader impacts on air quality monitoring and exposure assessment.